Electrical sockets of the two-conductor type normally found in conventional electrical wall receptacles and electrical extension cords generally include an insulated housing and a pair of transversely spaced, longitudinally elongate, electrically conductive, contact bars or strips therein. In three-conductor type sockets a grounded contact member is provided in addition to the transversely spaced contact bars. The contact bars of both types of sockets are generally parallel to one another and are provided either with flexed, slightly bowed, central portions or with flexed re-entrant, or bent-back, portions so that when the contact blades of electrical plugs are inserted into the socket, the flat faces of the blades and bars abut one another and the flexed portions of the bars tend to frictionally retain the blades in the socket by pressing them against the insulated housing.
Although the foregoing arrangement provides some degree of protection for users of an electrical appliance or tool to which the electrical cord and plug are connected by tending to retain the plug in the socket against disconnecting forces due to gravity and due to minor tugs made on the electrical cord by the user, a significant safety threat still remains because live plug contact bars may be exposed to the user's grasp when he or she tries to disconnect the plug from the socket. Moreover, annoying inconvenience may be encountered by users in having to reinsert inadvertently disconnected plugs. These problems have caused considerable thought to be given to the development of electrical sockets that have releasable locking mechanisms therein which lock the contact blades of electrical plugs more securely to the interiors of the sockets.
One commonly used approach for providing improved retention of the plug contact blades in the sockets has been to provide transversely movable, spring-urged detent balls in the insulated housing of the socket. These balls cooperate with corresponding detent apertures in the plug contact blades. When the plug blades are then inserted into the sockets, the balls enter the apertures in the plug blades and thereby hold the plugs in the sockets more securely than in the earlier cases. One example of such detent type electrical socket may be seen in U.S. Pat. No. 2,198,504 to A. R. Pool. Related approaches, employing extra spring pressure to hold the contact blades and contact bars more firmly together, are shown in U.S. Pat. Nos. 2,213,020 to L. A. Scott and 4,700,997 to J. E. Strand. Although providing somewhat better retention, these arrangements still allow inadvertent withdrawal of the plugs when the electrical cords are tugged and as the resilience of the springs used therein decays with age.
Another approach for more securely locking the plugs to the sockets has been to provide transversely extending, movable pins in the socket housing or on the socket contact bars, and corresponding apertures on the plug contact blades. When the plug blades are then inserted into the sockets, the pins enter the apertures in the plug blades, either by camming or by spring action, and thereby hold the plugs in the sockets until the pins are physically withdrawn from the apertures by de-camming or other manipulation. Examples of such electrical sockets may be seen in U.S. Pat. Nos. 2,704,831 to W. R. Smith, 3,543,218 to A. M. Archer, and 4,136,919 to G. W. Howard et al. These arrangements also suffer from one or more of a number of disadvantages, such as being complex, costly, having short service lives and being inadaptable to use both in an electrical wall receptacle environment and in an extension cord environment.
Non-electrical sockets having releaseable electrical plug-locking mechanisms therein are also well known. Such sockets are employed to temporarily disable electrical plugs by preventing them from being connected to electrical sockets in order to preclude unauthorized use of the electrical equipment attached to the plugs. Examples of such non-electrical sockets may be seen in U.S. Pat. Nos. 3,543,544 to E. N. Efston and 4,566,297 to R. C. Hawley. These sockets, of course, are not useable as electrical sockets since they have no electrical contact bars therein.
It is, therefore, a primary object of this invention to provide an electrical socket having a releasable plug-locking mechanism that overcomes many of the disadvantages associated with prior known sockets.
Another object of this invention is to provide an electrical socket having a releasable plug-locking mechanism therein that employs a simple, positive, locking arrangement and that will operate effectively over a long, relatively trouble-free, service life.
Further objects and advantages of this invention will become apparent as the following description proceeds.